Atherosclerosis is the progressive narrowing and hardening of arteries over time. The process is characterized by plaque buildup on the inside of the arteries. Atherosclerosis is known to occur to some degree with aging, but other risk factors that accelerate this process have been identified, including high cholesterol, high blood pressure, smoking, diabetes and a family history for atherosclerotic disease.
Percutaneous transluminal coronary angioplasty is a common procedure used by doctors to treat atherosclerosis. The procedure involves mechanically dilating a narrowed or totally-obstructed artery by passing a balloon catheter through the artery to the area of plaque buildup and inflating the balloon, which compresses the plaque and increases the interior diameter of the artery. Doctors generally use a guide-wire across the arterial blockage to advance the balloon catheter to the site of the blockage.
During angioplasty, doctors may also place a stent in the newly widened artery to hold up the artery and decrease the risk of restenosis or re-narrowing of the artery. Stent installation generally follows the same angioplasty procedure, except the balloon is attached to a stent and together they are positioned at the site of blockage using a guide-wire. The balloon is then inflated to push the stent against the artery wall, which anchors the stent in place. The balloon is then deflated and removed along with the catheter and the guide-wire.
Although the use of a stent during angioplasty is generally preferred, doctors have found it difficult, if not impossible, to safely and effectively deploy the stent in bifurcated arteries—arteries divided into two equally important branches or, alternatively, a main artery branch giving away to a side branch. Specifically, inflating the balloon and pushing the stent against the artery wall in one branch may force plaque into the other branch of the artery, effectively blocking that branch, which could cause a heart attack if the artery supplies blood to the heart or a stroke if the artery supplies blood to the brain.
Alternatively, doctors have tried to use two guide-wires (one in each arterial branch) so that a balloon can be advanced to each branch and inflated either substantially simultaneously or in closely spaced intervals. In the event a stent is advanced into a bifurcation lesion after both branches have been dilated, the guide-wire not used for placement of the stent must be removed because the guide-wire would become permanently trapped in the arterial wall when the stent is deployed. Additionally, if the second guide-wire, which was not used for stenting, is removed and the stent is deployed using the first guide wire, some of the plaque residue can be squeezed into the side branch creating a blockage.